Grinding tools of the above-mentioned type can not only be used in dry but also in wet grinding processes. The application areas are the machining of natural and artificial stone, with grinding tools preferably made of several pieces in, for example, grinding and polishing stations for decorative stone materials, with production and repair grinding of tools for metal cutting machining which completely or partly consists of hardened tool steel, carbide or ceramics.
The patent document U.S. Pat. No. 3,650,715 indicates a grinding wheel bond which contains dendritic metal as filler in polyimide resin. The metal is in "clusters of dendritic metal particles," or as accumulations of dendrites. The above-mentioned patent document proposes heat-resistant polyimide resin for use in grinding tools subject to high stresses especially for dry grinding applications. To dissipate the heat arising with grinding and for the additional support of the abrasive grains in the resinoid bond matrix, copper and silver are preferred mixed in as filler. As a result, grinding wheels are proposed by which the soft contact of resinoid bonded grinding wheels and the thermal conductivity and stability of metal bonds are striven for in one tool.
A part of the resinoid bonded diamond grinding wheels for high heat stress or for high surface pressure on the abrasive coating, obtainable on the market, are based on the proposed bond type in the U.S. Pat. No. 3,650,715 patent.
The Japanese publication JP-A-516074 (Sintocogio Ltd.) describes a grinding wheel with higher density and strength, by which with the use of super abrasive no dimensional deviation is produced on the material to be machined. At the same time thermoplastic, temporary binder with a mixture of super abrasive and metal powder are heated in such a way that the thermoplastic binder is initially softened then liquified and granulated during the tempering. The granulated mixture is heated up once again in the mold up to liquefaction in order to obtain the "green" grinding wheel. The "green" wheel is sintered after the removal of the temporary binder.
U.S. Pat. No. 4,369,046A describes the combined shaping of both parts of a grinding wheel, namely the resinoid bonded abrasive coating and the metal bonded core, in order to then obtain a uniform grinding wheel. The inventors were confronted by problems well-known to technical specialists concerning very different tasks of abrasive coating and core, with their very different material characteristics. Accordingly, the subject matter of this invention is a combined shaped article with a resinoid bonded phase and a metal bonded phase, whereby the resinoid bonded phase is intended for the abrasive coating and the metal bonded phase for the core, and a volume percentile of the powder of each phase can be mixed to the other phase. The volume percentile of one phase in the other phase should as a result only move between 0-30%.
A further subject matter of this invention is an accompanying process for the combined shaping of grinding wheels with a resinoid bonded phase and a metal bonded phase through simultaneous application of heat and pressure on both mixtures which are to be molded, for the abrasive coating and for the core.
In fact, in the U.S. Pat. No. 4,369,046A mixtures from one component are proposed with the other component, however, only as filler and in order to reduce the sudden transition of the characteristic profile in the separation zone from abrasive coating to core. This guarantee the processibility of components with inevitably very different characteristics which interfere with each other, on which the increasing of the melting point of the metal powder for the core points to at least 100.degree. C. over the molding temperature.